1. Field of the Invention
This invention relates to a method and apparatus for acquiring a fluorescence image, wherein intrinsic fluorescence, which is produced from living body tissues when the living body tissues are exposed to excitation light, is acquired as an image. This invention also relates to a fluorescence imaging apparatus for imaging fluorescence, which is produced from a measuring site when the measuring site is exposed to excitation light.
2. Description of the Related Art
Research has heretofore been conducted with respect to techniques, wherein intrinsic fluorescence, which is produced by an intrinsic dye in living body tissues when excitation light is irradiated to the living body tissues, is detected as an image, the image having been formed with the intrinsic fluorescence is analyzed, and a change in tissue condition of the living body tissues due to various kinds of diseases is discriminated in accordance with the results of the analysis.
The intrinsic fluorescence produced from the living body tissues is weak, and image sensors having a high sensitivity have heretofore been utilized for detecting the weak intrinsic fluorescence as an image. For example, in order for the intrinsic fluorescence to be imaged, there have heretofore been utilized high-sensitivity CCD (charge coupled device) image sensors, which are capable of performing pixel binning, i.e. processing for integrating signal charges of a plurality of pixels in each of CCD image sensor chips and reading the integrated signal charges. Also, electron multiplication types of image sensors, such as ICCD""s, have heretofore been utilized to image the intrinsic fluorescence.
By way of example, the excitation light may be irradiated to living body tissues in the body cavity having a complicated shape, or the like, and a fluorescence image of the intrinsic fluorescence produced from the living body tissues may be acquired by utilizing an endoscope system. In such cases, it is desired that the intrinsic fluorescence produced from diseased tissues, such as cancerous tissues, which are located at a position (i.e., a remote point) spaced 50 mm apart from a leading end of a measuring probe of the endoscope system, be detected with a signal-to-noise ratio of at least 1.
However, in cases where the technique for performing the pixel binning is utilized, when the signal charges occurring in a plurality of pixels having received the intrinsic fluorescence are integrated in each of the CCD image sensor chips, electric charges occurring due to dark noise, which is contained in the signal charges accumulated in the pixels to be subjected to the pixel binning, are integrated together with the signal charges.
Therefore, since the intrinsic fluorescence produced from the cancerous tissues is weak, it often occurs that the number of electric charges occurring in each pixel due to the dark noise is larger than the number of electric charges occurring in each pixel due to the receiving of the intrinsic fluorescence. In such cases, even if the signal charges having been accumulated in the plurality of pixels are integrated with the pixel binning, the level of the signal representing the intrinsic fluorescence produced from the cancerous tissues will become lower than the level of the signal due to the dark noise. Therefore, the signal-to-noise ratio cannot be enhanced and will become lower than 1. Also, in cases where the electron multiplication types of image sensors are utilized, if the setting of the image sensor is not performed sufficiently accurately, it will often occur that the intrinsic fluorescence produced from the cancerous tissues located at the aforesaid remote point cannot be detected with a signal-to-noise ratio of at least 1 due to the occurrence of the dark noise and reading noise.
Further, it is desired that the intrinsic fluorescence produced from normal tissues, which are located at a position (i.e., a near point) spaced 5 mm apart from the leading end of the measuring probe of the endoscope system, be detected such that saturation may not be reached in a light receiving capacity of an imaging apparatus.
However, dynamic ranges of the electron multiplication types of image sensors, such as ICCD""s, are narrower than the order of 101. Therefore, if the setting of the image sensor is not performed sufficiently accurately, saturation will be reached in the light receiving capacity of the imaging apparatus. In cases where the technique for performing the pixel binning is utilized, as for the pixels in a region in which the intensity of received light is high, the number of pixels subjected to the pixel binning may be set at a small value. In this manner, the number of pixels subjected to the pixel binning may be set in accordance with the intensity of received light. However, in such cases, if the setting of the image sensor is not performed sufficiently accurately, the problems will occur in that saturation will be reached in the light receiving capacity of the imaging apparatus.
The primary object of the present invention is to provide a method of acquiring a fluorescence image, wherein an image of intrinsic fluorescence produced from a measuring site of living body tissues located at a remote point is capable of being acquired with a high signal-to-noise ratio.
Another object of the present invention is to provide a method of acquiring a fluorescence image, wherein an image of intrinsic fluorescence produced from a measuring site of living body tissues located at a near point is capable of being acquired such that saturation is not reached in light receiving capacity of an imaging apparatus.
A further object of the present invention is to provide an apparatus for carrying out the method of acquiring a fluorescence image.
A still further object of the present invention is to provide a fluorescence imaging apparatus, wherein reading noise is capable of being suppressed and a signal-to-noise ratio of a detected image is capable of being enhanced, such that adverse effects do not occur on displaying of a fluorescence image as a dynamic image.
The present invention provides a first method of acquiring a fluorescence image, comprising the steps of:
i) detecting intrinsic fluorescence, which has been produced from living body tissues when excitation light is irradiated to the living body tissues, with an image sensor, the excitation light causing the living body tissues to produce the intrinsic fluorescence, and
ii) reading out the detected intrinsic fluorescence as an image,
wherein the image is acquired by setting the image sensor such that a reading frequency, an area of one pixel, a total number of pixels, a number of pixels subjected to pixel binning, a number of reading ports, an exposure time, a quantum efficiency, an electron multiplication factor, and a sensor temperature of the image sensor satisfy the following condition formula:
RN+DN less than 0.22xc3x97Pxc3x97Hxc3x97G
The present invention also provides a second method of acquiring a fluorescence image, comprising the steps of:
i) detecting intrinsic fluorescence, which has been produced from living body tissues when excitation light is irradiated to the living body tissues, with an image sensor, the excitation light causing the living body tissues to produce the intrinsic fluorescence, and
ii) reading out the detected intrinsic fluorescence as an image,
wherein the image is acquired by setting the image sensor such that a reading frequency, an area of one pixel, a total number of pixels, a number of pixels subjected to pixel binning, a number of reading ports, an exposure time, a quantum efficiency, an electron multiplication factor, a sensor temperature, a floating diffusion capacity, and a full well capacity of the image sensor satisfy the following condition formulas:
(RN+DN)xc3x971000xc3x97G less than Fd
(RN+DN)xc3x971000xc3x97G less than Fw
The present invention further provides a first apparatus for acquiring a fluorescence image, comprising:
i) an image sensor for detecting intrinsic fluorescence, which has been produced from living body tissues when excitation light is irradiated to the living body tissues, the excitation light causing the living body tissues to produce the intrinsic fluorescence, and
ii) read-out means for reading out the detected intrinsic fluorescence as an image,
wherein the image sensor is set such that a reading frequency, an area of one pixel, a total number of pixels, a number of pixels subjected to pixel binning, a number of reading ports, an exposure time, a quantum efficiency, an electron multiplication factor, and a sensor temperature of the image sensor satisfy the following condition formula:
RN+DN less than 0.22xc3x97Pxc3x97Hxc3x97G
The present invention still further provides a second apparatus for acquiring a fluorescence image, comprising:
i) an image sensor for detecting intrinsic fluorescence, which has been produced from living body tissues when excitation light is irradiated to the living body tissues, the excitation light causing the living body tissues to produce the intrinsic fluorescence, and
ii) read-out means for reading out the detected intrinsic fluorescence as an image,
wherein the image sensor is set such that a reading frequency, an area of one pixel, a total number of pixels, a number of pixels subjected to pixel binning, a number of reading ports, an exposure time, a quantum efficiency, an electron multiplication factor, a sensor temperature, a floating diffusion capacity, and a full well capacity of the image sensor satisfy the following condition formulas:
(RN+DN)xc3x971000xc3x97G less than Fd
(RN+DN)xc3x971000xc3x97G less than Fw
In the first and second apparatuses for acquiring a fluorescence image in accordance with the present invention, the reading frequency may be set so as to satisfy the condition RN=DN.
Also, in the first and second apparatuses for acquiring a fluorescence image in accordance with the present invention, the image sensor may be a CCD type of image sensor or a MOS (metal oxide semiconductor) type of image sensor.
In the formulas described above, RN represents the number of electric charges occurring due to reading noise (which number is determined by the reading frequency and the area of one pixel), DN represents the number of electric charges occurring due to dark noise (which number is determined by the reading frequency, the area of one pixel, the total number of pixels, the number of pixels subjected to pixel binning, the number of reading ports, the exposure time, and the sensor temperature), P represents the irradiation output of the excitation light (in mW), H represents the quantum efficiency of the image sensor, G represents the electron multiplication factor of the image sensor, Fd represents the number of electric charges corresponding to the floating diffusion capacity, and Fw represents the number of electric charges corresponding to the full well capacity.
Also, RN and DN may be represented by the formulas shown below.
RN=0.17S0.777xc3x97fxc2xd
DN=(tread+texp)xc3x97Sxc3x97nxc3x97ed(T)
tread=(N/n)/(fxc3x97106xc3x97M)+{(nxe2x88x921)xc3x97(N/n)}/(fxc3x97107xc3x97M)
d(T)=4.1913xc3x9710xe2x88x926xc3x97(273+T)3xe2x88x923.8015xc3x9710xe2x88x923xc3x97(273+T)2+1.2197xc3x97(273+T)xe2x88x92136
in which S represents the area of one pixel (in xcexcm2), f represents the reading frequency (in megapixel/sec), N represents the total number of pixels, n represents the number of pixels subjected to pixel binning, M represents the number of reading ports, texp represents the exposure time (in sec), and T represents the temperature of the image sensor (in xc2x0 C.).
In the first and second methods of acquiring a fluorescence image in accordance with the present invention and the first and second apparatuses for acquiring a fluorescence image in accordance with the present invention, the image may be acquired as images, which are acquired successively for every {fraction (1/30)} second per image frame as in ordinary cases. Alternatively, the image may be acquired as images, which are acquired successively, for example, for every {fraction (1/10)} second per image frame such that, even if the motion of the detected images cannot be seen as a smooth motion, the measuring site is capable of being seen successively.
The term xe2x80x9cnumber of electric charges corresponding to a capacityxe2x80x9d as used herein means the value obtained by converting each of the floating diffusion capacity Fd and the full well capacity Fw into the number of electric charges in order to true up the units in the aforesaid formulas as the number of electric charges.
The first and second methods of acquiring a fluorescence image in accordance with the present invention may be combined with each other. Also, first and second apparatuses for acquiring a fluorescence image in accordance with the present invention may be combined with each other. Specifically, the image may be acquired by setting the image sensor such that the reading frequency, the area of one pixel, the total number of pixels, the number of pixels subjected to pixel binning, the number of reading ports, the exposure time, the quantum efficiency, the electron multiplication factor, the sensor temperature, the floating diffusion capacity, and the full well capacity of the image sensor satisfy the three condition formulas shown above, i.e. the following condition formulas:
RN+DN less than 0.22xc3x97Pxc3x97Hxc3x97G
(RN+DN)xc3x971000xc3x97G less than Fd
(RN+DN)xc3x971000xc3x97G less than Fw
The present invention also provides a fluorescence imaging apparatus, comprising:
i) irradiation means for irradiating excitation light to a measuring site, the excitation light causing the measuring site to produce fluorescence, and
ii) imaging means for detecting the fluorescence, which has been produced from the measuring site, the imaging means being provided with an imaging surface, which comprises a plurality of pixels arrayed in a two-dimensional form,
wherein the imaging means is provided with a plurality of output ports.
In the fluorescence imaging apparatus in accordance with the present invention, the imaging means may be one of various types of means provided with the imaging surface, which comprises a plurality of pixels arrayed in a two-dimensional form. For example, the imaging means may be an ordinary CCD image sensor, a MOS type of image sensor, a back surface incidence type of image sensor which is capable of performing high-sensitivity imaging, or a multiplication type of image sensor combined with multiplication means.
The fluorescence imaging apparatus in accordance with the present invention should preferably be modified such that the imaging surface is divided into N number of imaging blocks, where N is at least 2,
each of the output ports is provided for one of the N number of imaging blocks, and
the fluorescence imaging apparatus further comprises:
composing means for combining image signals, which have been outputted from the output ports, to form an image signal representing one image,
correction value calculating means for calculating correction values in accordance with variations in output characteristics among N number of output channels, which extend from the N number of imaging blocks to the composing means,
correction means for performing compensation for the variations in output characteristics, and
correction value setting means for setting the correction values in the correction means.
In such cases, the correction means should preferably be constituted of signal transforming means, which stores offset values and tone curve correction values.
Also, the fluorescence imaging apparatus in accordance with the present invention, wherein the correction means is constituted of the signal transforming means, should preferably be modified such that the imaging surface of the imaging means is constituted of an image exposure region and non-exposure regions,
each of the imaging blocks contains one of the non-exposure regions,
the correction value calculating means calculates the offset values, which act as the correction values, from image signals having been detected in a state, in which light impinges upon the imaging surface of the imaging means, and having been outputted through the respective output channels, the offset values being calculated such that signal intensities of image signals, which have been detected respectively in the non-exposure regions of the imaging blocks, take approximately identical values, and
the correction value calculating means calculates the tone curve correction values, which act as the correction values, from the image signals having been detected in the state, in which light impinges upon the imaging surface of the imaging means, and having been outputted through the respective output channels, the tone curve correction values being calculated such that signal intensities of image signals, which have been detected respectively at adjacent ends of the imaging blocks that are adjacent to each other, take approximately identical values.
Further, the fluorescence imaging apparatus in accordance with the present invention, wherein the correction means is constituted of the signal transforming means, may be modified such that the correction value calculating means calculates the offset values, which act as the correction values, from image signals having been detected in a state, in which light is blocked from impinging upon the imaging surface of the imaging means, and having been outputted through the respective output channels, the offset values being calculated such that signal intensities of image signals, which have been detected respectively in the imaging blocks, take approximately identical values, and
the correction value calculating means calculates the tone curve correction values, which act as the correction values, from image signals having been detected in a state, in which light impinges upon the imaging surface of the imaging means, and having been outputted through the respective output channels, the tone curve correction values being calculated such that signal intensities of image signals, which have been detected respectively at adjacent ends of the imaging blocks that are adjacent to each other, take approximately identical values.
Furthermore, in the fluorescence imaging apparatus in accordance with the present invention, the correction means may be constituted of amplification means, in which offset values and gains are capable of being adjusted.
Also, the fluorescence imaging apparatus in accordance with the present invention, wherein the correction means is constituted of the amplification means, should preferably be modified such that the imaging surface of the imaging means is constituted of an image exposure region and non-exposure regions,
each of the imaging blocks contains one of the non-exposure regions,
the correction value calculating means calculates the offset values, which act as the correction values, from image signals having been detected in a state, in which light impinges upon the imaging surface of the imaging means, and having been outputted through the respective output channels, the offset values being calculated such that signal intensities of image signals, which have been detected respectively in the non-exposure regions of the imaging blocks, take approximately identical values, and
the correction value calculating means calculates gain adjustment values, which act as the correction values, from the image signals having been detected in the state, in which light impinges upon the imaging surface of the imaging means, and having been outputted through the respective output channels, the gain adjustment values being calculated such that signal intensities of image signals, which have been detected respectively at adjacent ends of the imaging blocks that are adjacent to each other, take approximately identical values.
Further, the fluorescence imaging apparatus in accordance with the present invention, wherein the correction means is constituted of the amplification means, may be modified such that the correction value calculating means calculates the offset values, which act as the correction values, from image signals having been detected in a state, in which light is blocked from impinging upon the imaging surface of the imaging means, and having been outputted through the respective output channels, the offset values being calculated such that signal intensities of image signals, which have been detected respectively in the imaging blocks, take approximately identical values, and
the correction value calculating means calculates the gain adjustment values, which act as the correction values, from image signals having been detected in a state, in which light impinges upon the imaging surface of the imaging means, and having been outputted through the respective output channels, the gain adjustment values being calculated such that signal intensities of image signals, which have been detected respectively at adjacent ends of the imaging blocks that are adjacent to each other, take approximately identical values.
Furthermore, the fluorescence imaging apparatus in accordance with the present invention should preferably be modified such that the imaging surface of the imaging means is constituted of an image exposure region and non-exposure regions,
the fluorescence imaging apparatus further comprises re-setting judgment means for making a judgment for each imaging operation and as to whether re-setting of the correction values is to be or is not to be performed, the judgment being made in accordance with the presence or absence of a change in signal intensity of an image signal, which has been detected in one of the non-exposure regions,
the correction value calculating means operates such that, in cases where it has been judged by the re-setting judgment means that the re-setting of the correction values is to be performed, the correction value calculating means calculates new correction values, and
the correction value setting means sets the new correction values, which have been calculated by the correction value calculating means, as the correction values in the correction means.
As described above, the judgment as to whether the re-setting of the correction values is to be or is not to be performed is made in accordance with the presence or absence of a change in signal intensity of an image signal, which has been detected in one of the non-exposure regions. For example, in cases where a change occurs in a mean value of signal intensities of the image signal, which has been detected in one of the non-exposure regions, or in cases where a change occurs in the signal intensity corresponding to a predetermined site, or the like, it is judged that the re-setting of the correction values is to be performed. In cases where such a change does not occur, it is judged that the correction values are not to be altered.
Also, the fluorescence imaging apparatus in accordance with the present invention may be modified such that the imaging surface is divided into N number of imaging blocks, where N is at least 2,
each of the output ports is provided for one of the N number of imaging blocks, and
the fluorescence imaging apparatus further comprises:
composing means for combining image signals, which have been outputted from the output ports, to form an image signal representing one image,
correction value storing means for storing correction values for compensation for variations in output characteristics, the correction values having been calculated in accordance with the variations in output characteristics among N number of output channels, which extend from the N number of imaging blocks to the composing means,
correction means for performing compensation for the variations in output characteristics, and
correction value setting means for setting the correction values in the correction means.
In such cases, the correction means may be constituted of signal transforming means, which stores offset values and tone curve correction values. In such cases, the correction value storing means should preferably store the offset values and the tone curve correction values as the correction values.
Alternatively, the correction means may be constituted of amplification means, in which offset values and gains are capable of being adjusted. In such cases, the correction value storing means should preferably store the offset values and gain adjustment values as the correction values.
The fluorescence imaging apparatus in accordance with the present invention, wherein the correction value storing means is employed, should preferably be modified such that the correction value storing means stores signal intensity or a mean value of signal intensities of an image signal having been detected in a state, in which light is blocked from impinging upon the imaging surface of the imaging means, and corresponding correction values,
the fluorescence imaging apparatus further comprises re-setting judgment means for making a judgment for each imaging operation and as to whether re-setting of the correction values is to be or is not to be performed, the judgment being made in accordance with the presence or absence of a change in signal intensity or a mean value of signal intensities of an image signal having been detected in a state, in which light is blocked from impinging upon the imaging surface of the imaging means, and
the correction value setting means operates such that, in cases where it has been judged by the re-setting judgment means that the re-setting of the correction values is to be performed, the correction value setting means reads the correction values, which correspond to the signal intensity or the mean value of signal intensities of the image signal associated with the judgment in that the re-setting of the correction values is to be performed, from among the correction values having been stored in the correction value storing means and sets the correction values, which have thus been read from the correction value storing means, as the correction values in the correction means.
Also, the fluorescence imaging apparatus in accordance with the present invention, wherein the correction value storing means is employed, should preferably be modified such that the imaging surface of the imaging means is constituted of an image exposure region and non-exposure regions,
the correction value storing means stores signal intensity or a mean value of signal intensities of an image signal, which has been detected in one of the non-exposure regions, and corresponding correction values,
the fluorescence imaging apparatus further comprises re-setting judgment means for making a judgment for each imaging operation and as to whether re-setting of the correction values is to be or is not to be performed, the judgment being made in accordance with the presence or absence of a change in signal intensity or a mean value of signal intensities of an image signal, which has been detected in one of the non-exposure regions, and
the correction value setting means operates such that, in cases where it has been judged by the re-setting judgment means that the re-setting of the correction values is to be performed, the correction value setting means reads the correction values, which correspond to the signal intensity or the mean value of signal intensities of the image signal associated with the judgment in that the re-setting of the correction values is to be performed, from among the correction values having been stored in the correction value storing means and sets the correction values, which have thus been read from the correction value storing means, as the correction values in the correction means.
Further, the fluorescence imaging apparatus in accordance with the present invention, wherein the correction value storing means is employed, should preferably be modified such that the correction value storing means stores information representing a temperature in the vicinity of the imaging means and corresponding correction values, which have been calculated by the correction value calculating means,
the fluorescence imaging apparatus further comprises:
temperature detecting means for detecting the temperature in the vicinity of the imaging means, and
re-setting judgment means for making a judgment for each imaging operation and as to whether re-setting of the correction values is to be or is not to be performed, the judgment being made in accordance with the presence or absence of a change in temperature in the vicinity of the imaging means, and the correction value setting means operates such that, in cases where it has been judged by the re-setting judgment means that the re-setting of the correction values is to be performed, the correction value setting means reads the correction values, which correspond to the temperature in the vicinity of time imaging means associated with the judgment in that the re-setting of the correction values is to be performed, from among the correction values having been stored in the correction value storing means and sets the correction values, which have thus been read from the correction value storing means, as the correction values in the correction means.
In the fluorescence imaging apparatus in accordance with the present invention, the value of N should preferably be at most 64, and should more preferably be at most 8.
With the first method of acquiring a fluorescence image and the first apparatus for acquiring a fluorescence image in accordance with the present invention, in which the intrinsic fluorescence having been detected by the image sensor is acquired as the image, the image sensor is set so as to satisfy the condition formula:
RN+DN less than 0.22xc3x97Pxc3x97Hxc3x97G
Therefore, the number of electric charges occurring in the imaging apparatus due to dark noise and reading noise is restricted to be smaller than the number of electric charges occurring in the imaging apparatus due to the intrinsic fluorescence produced from the measuring site. Accordingly, the fluorescence image is capable of being acquired with a high signal-to-noise ratio.
With the second method of acquiring a fluorescence image and the second apparatus for acquiring a fluorescence image in accordance with the present invention, in which the intrinsic fluorescence having been detected by the image sensor is acquired as the image, the image sensor is set so as to satisfy the condition formulas:
(RN+DN)xc3x971000xc3x97G less than Fd
(RN+DN)xc3x971000xc3x97G less than Fw
Therefore, the floating diffusion capacity and the full well capacity of the imaging apparatus are capable of taking sufficiently large values in comparison with the number of electric charges occurring in the imaging apparatus due to dark noise and reading noise. As a result, the fluorescence image is capable of being acquired such that saturation is not reached in the light receiving capacity of the imaging apparatus.
With the first and second apparatuses for acquiring a fluorescence image in accordance with the present invention, wherein the reading frequency f of the image sensor is set so as to satisfy the condition RN=DN, the sum of the number of electric charges occurring due to dark noise and the number of electric charges occurring due to reading noise is capable of being minimized.
Also, with the first and second apparatuses for acquiring a fluorescence image in accordance with the present invention, wherein the image sensor is the CCD type of image sensor or the MOS type of image sensor, the space for the image sensor is capable of being kept small.
With the fluorescence imaging apparatus in accordance with the present invention, wherein the imaging means is provided with a plurality of output ports, the number of pixels allocated to one output port is capable of being reduced to one-half or less in comparison with the cases where the imaging means is provided with only a single output port. Therefore, even if the reading frequency is set at a low value, signal charges of all pixels are capable of being read within the reading time. Accordingly, reading noise is capable of being suppressed and the signal-to-noise ratio of the detected image is capable of being enhanced, such that adverse effects do not occur on displaying of the fluorescence image as a dynamic image.
In cases where the imaging surface is divided into N number of imaging blocks, where N is at least 2, and each of the output ports is provided for one of the N number of imaging blocks, the imaging means provided with a plurality of output ports can be formed easily. However, in such cases, the uniformity of the characteristics of the output system, which uniformity an image sensor naturally has, is lost. Specifically, variations in output characteristics will occur among N number of output channels, which extend from the N number of imaging blocks to the composing means for composing an image signal representing one image from the image signals having been outputted from the output ports, and division line patterns will appear in the formed image. However, with the fluorescence imaging apparatus in accordance with the present invention, the correction values are calculated in accordance with variations in output characteristics among N number of output channels, which extend from the N number of imaging blocks to the composing means. Also, the calculated correction values are set in the correction means for performing compensation for the variations in output characteristics. Therefore, the variations in output characteristics are capable of being compensated for, and the problems are capable of being prevented from occurring in that division line patterns appear in the formed image.
With the fluorescence imaging apparatus in accordance with the present invention, wherein the correction means is constituted of the signal transforming means, which stores the offset values and the tone curve correction values, the compensation for the output characteristics is capable of being performed easily.
With the fluorescence imaging apparatus in accordance with the present invention, wherein each of the imaging blocks contains one of the non-exposure regions, the offset values and the tone curve correction values, which act as the correction values, are capable of being calculated from the image signals having been detected in the state, in which light impinges; upon the imaging surface of the imaging means. Therefore, the calculations of the correction values are capable of being made such that the ordinary imaging operation is not obstructed.
With the fluorescence imaging apparatus in accordance with the present invention, the offset values, which act as the correction values, may be calculated from the image signals having been detected in the state, in which light is blocked from impinging upon the imaging surface of the imaging means, and the tone curve correction values, which act as the correction values, may be calculated from the image signals having been detected in the state, in which light impinges upon the imaging surface of the imaging means. In such cases, all of the imaging blocks need not necessarily contain the non-exposure regions, and therefore the flexibility in manner of division of the imaging blocks is capable of being enhanced.
With the fluorescence imaging apparatus in accordance with the present invention, wherein the correction means is constituted of the amplification means, in which the offset values and the gains are capable of being adjusted, amplification means, which has heretofore been provided in a signal processing circuit, can be utilized as the correction means. Therefore, new circuit parts need not be provided, and the production cost is capable of being kept low.
Also, with the fluorescence imaging apparatus in accordance with the present invention, wherein each of the imaging blocks contains one of the non-exposure regions, the offset values and the gain adjustment values, which act as the correction values, are capable of being calculated from the image signals having been detected in the state, in which light impinges upon the imaging surface of the imaging means. Therefore, the calculations of the correction values are capable of being made such that the ordinary imaging operation is not obstructed.
With the fluorescence imaging apparatus in accordance with the present invention, the offset values, which act as the correction values, may be calculated from the image signals having been detected in the state, in which light is blocked from impinging upon the imaging surface of the imaging means, and the gain adjustment values, which act as the correction values, may be calculated from the image signals having been detected in the state, in which light impinges upon the imaging surface of the imaging means. In such cases, all of the imaging blocks need not necessarily contain the non-exposure regions, and therefore the flexibility in manner of division of the imaging blocks is capable of being enhanced.
It has been known that the output characteristics of the output channels vary for different ambient temperatures. Also, the image signal, which has been detected in the non-exposure region of the imaging surface of the imaging means, is the one primarily due to dark current and varies for different ambient temperatures. Therefore, if no change occurs in signal intensity of the image signal, which has been detected in the non-exposure region of the imaging surface of the imaging means, it can be regarded that no change occurs in output characteristics. Accordingly, a change in signal intensity of the image signal, which has been detected in one of the non-exposure regions, may be investigated for each imaging operation. In cases where no change in signal intensity occurs, it may be regarded that no change occurs in output characteristics, and corrections may be made by utilizing the correction values, which have already been set in the correction means. In this manner, the number of times of calculations of new correction values is capable of being reduced, and the processing time required to make the compensation for the output characteristics is capable of being kept short.
With the fluorescence imaging apparatus in accordance with the present invention, wherein the correction value storing means is employed, the correction values, which have been calculated in accordance with the variations in output characteristics among N number of output channels extending from the N number of imaging blocks to the composing means and which have been stored in the correction value storing means, may be set in the correction means for performing compensation for the variations in output characteristics. Therefore, the number of pixels allocated to one output port is capable of being reduced to a value smaller than in cases where the imaging means is provided with only a single output port. Therefore, even if the reading frequency is set at a low value, signal charges of all pixels are capable of being read within the reading time. Accordingly, reading noise is capable of being suppressed and the signal-to-noise ratio of the detected image is capable of being enhanced, such that adverse effects do not occur on displaying of the fluorescence image as a dynamic image. Also, the variations in output characteristics are capable of being compensated for, and the problems are capable of being prevented from occurring in that division line patterns appear in the formed image, such that adverse effects do not occur on displaying of the fluorescence image as a dynamic image.
With the fluorescence imaging apparatus in accordance with the present invention, wherein the correction value storing means is employed, the correction means may be constituted of the signal transforming means, which stores the offset values and the tone curve correction values, and the correction value storing means may store the offset values and the tone curve correction values as the correction values. In such cases, the compensation for the output characteristics is capable of being made easily.
With the fluorescence imaging apparatus in accordance with the present invention, wherein the correction means is constituted of the amplification means, in which the offset values and the gains are capable of being adjusted, and the correction value storing means stores the offset values and gain adjustment values as the correction values, amplification means, which has heretofore been provided in a signal processing circuit, can be utilized as the correction means. Therefore, new circuit parts need not be provided, and the production cost is capable of being kept low.
With the fluorescence imaging apparatus in accordance with the present invention, wherein the correction value storing means is employed, the correction value storing means may store the signal intensity or the mean value of signal intensities of the image signal having been detected in the state, in which light is blocked from impinging upon the imaging surface of the imaging means, and the corresponding correction values. Also, for each imaging operation, a change of the signal intensity or the mean value of signal intensities of the image signal having been detected in the state, in which light is blocked from impinging upon the imaging surface of the imaging means, may be investigated. In cases where a change of the signal intensity or the mean value of signal intensities of the image signal occurs, the correction values, which correspond to the signal intensity or the mean value of signal intensities of the image signal associated with the judgment in that the re-setting of the correction values is to be performed, may be read from among the correction values having been stored in the correction value storing means and may be set as the correction values in the correction means. In such cases, the processing for calculating the correction values is capable of being omitted, and the processing time required to make the compensation for the output characteristics is capable of being kept short.
With the fluorescence imaging apparatus in accordance with the present invention, wherein the correction value storing means is employed, the correction value storing means may store the signal intensity or the mean value of signal intensities of the image signal, which has been detected in one of the non-exposure regions, and corresponding correction values. Also, for each imaging operation, a change of the signal intensity or the mean value of signal intensities of the image signal, which has been detected in one of the non-exposure regions, may be investigated. In cases where a change of the signal intensity or the mean value of signal intensities of the image signal occurs, the correction values, which correspond to the signal intensity or the mean value of signal intensities of the image signal associated with the judgment in that the re-setting of the correction values is to be performed, may be read from among the correction values having been stored in the correction value storing means and may be set as the correction values in the correction means. In such cases, the processing for calculating the correction values is capable of being omitted, and the processing time required to make the compensation for the output characteristics is capable of being kept short. Also, the change of the signal intensity or the mean value of signal intensities of the image signal, which has been detected in one of the non-exposure regions, can be detected by utilizing the ordinary imaging operation. Therefore, the processing for the compensation for the output characteristics is capable of being simplified.
With the fluorescence imaging apparatus in accordance with the present invention, wherein the correction value storing means is employed, the correction value storing means may store the information representing the temperature in the vicinity of the imaging means and the corresponding correction values, which have been calculated by the correction value calculating means, and the temperature detecting means for detecting the temperature in the vicinity of the imaging means may be provided. Also, for each imaging operation, a change in temperature in the vicinity of the imaging means may be investigated. In cases where a change in temperature occurs, the correction values, which correspond to the temperature in the vicinity of the imaging means associated with the judgment in that the re-setting of the correction values is to be performed, may be read from among the correction values having been stored in the correction value storing means and may be set as the correction values in the correction means. In such cases, the processing for calculating the correction values is capable of being omitted, and the processing time required to make the compensation for the output characteristics is capable of being kept short. Also, the acquisition and comparison of the temperature in the vicinity of the imaging means can be performed with simple processing. Therefore, the processing for the compensation for the output characteristics is capable of being simplified even further.
With the fluorescence imaging apparatus in accordance with the present invention, wherein the value of N, i.e. the number of division of the imaging surface, falls within the range of 2 to 64, the reading frequency is capable of being set at a low value, and reading noise is capable of being suppressed, such that peripheral circuits and the compensation processing may not become complicated. Also, in cases where the value of N, i.e. the number of division of the imaging surface, falls within the range of 2 to 8, the peripheral circuits and the compensation processing are capable of being simplified even further.